Communication system and communication apparatus controlling a switching hub for power saving

ABSTRACT

A CPU of an image forming apparatus controls, according to establishment of a sleep change condition, a MAC/PHY in a network unit to change the image forming apparatus from a link-up state to a link-down state. The CPU controls the image forming apparatus to change from a normal mode to a deep sleep mode. A CPU of the network unit controls, according to the change of the image forming apparatus from the normal mode to the deep sleep mode, the MAC/PHY to change the link-down state of the image forming apparatus to the link-up state. The CPU controls the MAC/PHY to transmit a MAC address necessary for causing the image forming apparatus to participate in VLAN to a switching hub.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation of U.S. patent applicationSer. No. 15/817,053, filed Nov. 17, 2017, which is a Continuation ofU.S. patent application Ser. No. 13/298,016 filed on Nov. 16, 2011, nowU.S. Pat. No. 9,853,821, which is a Continuation of U.S. patentapplication Ser. No. 12/465,231 filed May 13, 2009, now U.S. Pat. No.8,081,638, which claims priority from Japanese Patent Application No.2008-125876 filed May 13, 2008, the entire contents of each of which arehereby incorporated by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a communication system and acommunication apparatus.

Description of the Related Art

A network interface card (NIC) has conventionally been used for enablinga communication apparatus to communicate with other communicationapparatuses via a network such as a local area network (LAN).

Ethernet® is popular as a representative network standard. A NICcompliant with the Ethernet® standard can perform communication byselecting one of a plurality of communication speeds of 10 Mbps, 100Mbps, and 1000 Mbps.

Power saving has been required of the communication apparatus. In thisregard, for example, Japanese Patent Application Laid-Open No.2001-154763 discusses a technique for saving power by reducing acommunication speed of the NIC when the communication apparatus operatesin a power-saving mode.

To achieve more power saving, Japanese Patent Application Laid-Open No.2007-276341 discusses a technique for cutting off power supplied to apart of the communication apparatus when the communication apparatusoperates in the power-saving mode.

As a recent network related technique, a virtual local area network(VLAN) has been popular. This VLAN technique virtually divides aplurality of computer terminals physically connected to a network usinga network device such as a switching hub into a plurality of groups(virtual network) to manage the groups as they belong to different LANs.

The VLAN technique includes a dynamic VLAN technique. In the dynamicVLAN technique, the switching hub virtually divides a plurality ofcomputer terminals into a plurality of groups to manage them based oninformation (e.g., media access control (MAC) address) obtained fromeach of the plurality of computer terminals connected to the switchinghub.

Consideration will be given to a case where a communication link withthe switching hub is cut off in the communication apparatus connected tothe switching hub compliant with the dynamic VLAN technique. In thiscase, to reconnect (link-up) the communication link with the switchinghub, the communication apparatus has to transmit information such as aMAC address again to the switching hub.

It is because the switching hub compliant with the dynamic VLANtechnique has determined that the computer terminal having itscommunication link cut off no longer belongs to (participates in) theVLAN when the cutting-off of the communication link is performed. Toparticipate in the VLAN configured by the switching hub, thecommunication apparatus has to transmit information such as a MACaddress to the switching hub.

In this regard, Japanese Patent Application Laid-Open Nos. 2001-154763and 2007-276341 give no discussion about the dynamic VLAN technique.Thus, the techniques discussed in these two documents cannotsimultaneously achieve power saving of the communication apparatus andcomplying with the dynamic VLAN.

SUMMARY OF THE INVENTION

The present invention is directed to secure transmission of informationnecessary for a communication apparatus to participate in a virtualnetwork while achieving power saving of the communication apparatus.

According to an aspect of the present invention, a communication systemincludes a switching hub capable of configuring a virtual network, and acommunication apparatus connected to a network via the switching hub.The switching hub includes a first packet processing unit configured totransfer packet data with the communication apparatus, a storage unitconfigured to store identification information for identifying aterminal permitted to participate in the virtual network, and amanagement unit configured to manage, if information received by thefirst packet processing unit from the communication apparatus matchesthe identification information stored in the storage unit, thecommunication apparatus to participate in the virtual networkcorresponding to the matched identification information. Thecommunication apparatus includes a second packet processing unitconfigured to transfer the packet data with the switching hub, a firstcontrol unit configured to control the communication apparatus, a secondcontrol unit configured to control the second processing unit, a powersupply unit configured to supply power in one of a normal mode forsupplying power to the first control unit, the second control unit, andthe second packet processing unit and a power-saving mode for reducingpower supplied to the first control unit lower than power in the normalmode while supplying power to the second control unit and the secondpacket processing unit, and a first determination unit configured todetermine whether a switching condition for switching from the normalmode to the power-saving mode has been established. The first controlunit controls, according to the determination of the determination unitthat the switching condition has been established, the second packetprocessing unit to change from a link-up state where a communicationlink is established with the switching hub to a link-down state wherethe communication link is not established, and the power supply unit tochange from the normal mode to the power-saving mode. The second controlunit controls, according to the change from the normal mode to thepower-saving mode, the second packet processing unit to change thelink-down state to the link-up state and to transmit information neededby the switching hub to cause the communication apparatus to participatein the virtual network to the switching hub. The second packetprocessing unit sets a communication speed between the communicationapparatus and the switching hub when the power supply unit operates inthe power-saving mode lower than a communication speed between thecommunication apparatus and the switching hub when the power supply unitoperates in the normal mode.

Further features and aspects of the present invention will becomeapparent from the following detailed description of exemplaryembodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate exemplary embodiments, features,and aspects of the invention and, together with the description, serveto explain the principles of the invention.

FIG. 1 is a block diagram illustrating a configuration of acommunication system.

FIG. 2 is a block diagram illustrating a configuration of an imageforming apparatus.

FIG. 3 is a block diagram illustrating a configuration of a controlunit.

FIG. 4 illustrates a software configuration of a program executed by acentral processing unit (CPU).

FIG. 5 is a block diagram illustrating a configuration of a networkunit.

FIG. 6 illustrates a VLAN database in a MAC based VLAN.

FIG. 7 is a flowchart illustrating an operation executed by a CPU of thecontrol unit.

FIG. 8 is a flowchart illustrating an operation executed by a CPU of thenetwork unit.

FIG. 9 is a block diagram illustrating a configuration of a switchinghub.

FIG. 10 illustrates a VLAN database in a subnet based VLAN.

FIG. 11 illustrates a VLAN database in a user based VLAN.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Various exemplary embodiments, features, and aspects of the inventionwill be described in detail below with reference to the drawings.

In the drawings, elements and parts which are identical throughout theexemplary embodiments are designated by identical reference numerals,and duplicate description thereof is omitted.

Referring to the drawings, the exemplary embodiments of the presentinvention will be described. Components of the exemplary embodiments areonly examples, not limiting a scope of the present invention.

FIG. 1 is a block diagram illustrating a configuration of acommunication system which includes a communication apparatus accordingto a first exemplary embodiment of the present invention.

In FIG. 1, a communication system 1000 includes an image formingapparatus 1003 having an image output function, and personal computers(PCs) 1001 and 1002 as computer terminals. These components areconnected to a local area network (LAN) 1005 via a switching hub 1004.

The image forming apparatus 1003 includes an operation unit 1010 forallowing a user to perform various operations, a scanner unit 1008 forreading image information according to an instruction from the operationunit 1010, and a printer unit 1007 for printing image data on a sheet.The image forming apparatus 1003 further includes a control unit 1006for controlling the scanner unit 1008 and the printer unit 1007 based oninstructions from the operation unit 1010 and the PC 1002. Further, theimage forming apparatus 1003 includes a power supply unit 1009 forsupplying power to the image forming apparatus 1003.

The PCs 1001 and 1002 can transmit print jobs each containing one pageor a plurality of pages of image data to the image forming apparatus1003 via the LAN 1005. The PCs 1001 and 1002 can transmit, in additionto the print jobs, various commands to the image forming apparatus 1003.The PCs 1001 and 1002 can transmit the print jobs to not only the imageforming apparatus 1003 but also other image forming apparatusesconnected to the LAN 1005.

FIG. 2 is a block diagram illustrating a configuration of the imageforming apparatus 1003 illustrated in FIG. 1.

In FIG. 2, the scanner unit 1008 includes a platen glass 101 for placinga document, an automatic document feeder 142 for sequentially feedingdocuments to a predetermined position of the platen glass 101. Thescanner unit 1008 scans to expose the documents placed on the platenglass 101 in a main scanning direction. The scanner unit 1008 includes adocument illumination lamp 102, a scanning mirror 103, a scanning unit147 installed below the platen glass 101, and scanning mirrors 104 and105 for reflecting a reflected light from the scanning mirror 103 towarda charge coupled device (CCD) unit 106.

The scanner unit 1008 further includes a scanning unit 148 forperforming scanning in a sub-scanning direction at half the speed of thescanning unit 147, and an imaging lens 107 for receiving the reflectedlight from the scanning mirror 105 to form an image. The scanner unit1008 includes the CCD unit 106 including an imaging sensor 108constituted of a CCD for converting the formed image into, for example,an 8-bit digital image signal, and a CCD driver 109 for driving theimaging sensor 108.

The control unit 1006 receives an instruction from the operation unit1010, generates image data based on an image signal output from theimaging sensor 108, and controls the entire apparatus. The control unit1006 will be described below in detail referring to FIG. 3.

The printer unit 1007 exposes, based on image data generated by thecontrol unit 1006, the photosensitive drum 110 to form an electrostaticlatent image. For example, the printer unit 1007 includes an exposureunit 117 including a semiconductor laser, and a developing device 118for containing toner (i.e., black developer) and developing theelectrostatic latent image on the photosensitive drum 110 by the toner.The printer unit 1007 includes a pre-transfer charger 119 for applying ahigh voltage to the toner image developed on the photosensitive drum 110before transfer.

The printer unit 1007 includes a manual paper feeding unit 120, andpaper feeding units 122, 124, 142, and 144 for storing sheets. Theprinter unit 1007 includes feed rollers 121, 123, 125, 143, and 145 forfeeding sheets on the manual paper feeding unit 120 or sheets stored inthe paper feeding units 122, 124, 142, and 144. The printer unit 1007includes a registration roller 126 for feeding the sheets fed from thefeed rollers 121, 123, 125, 143 and 145 to the photosensitive drum 110.

The feed rollers 121, 123, 135, 143, and 145 temporarily stop the sheetson the manual feeding unit 120 or the sheets stored in the paper feedingunits 122, 124, 142, and 144 in a position of the registration roller126. Then, the feed rollers feed the sheets by taking write timing withthe toner image developed on the photosensitive drum 110.

The printer unit 1007 further includes a transfer charger 127 fortransferring the toner image developed on the photosensitive drum 110 tothe fed sheet, and a separation charger 128 for separating, from thephotosensitive drum 110, the sheet to which the toner image has beentransferred from the photosensitive drum 110.

The printer unit 1007 includes a conveyor belt 129 for conveying theseparated sheet to a fixing device 130, and a cleaner 11 for removingtoner left on the photosensitive drum 110. The printer unit 1007includes a pre-exposure lamp 112 for discharging the photosensitive drum110, and a primary charging unit 113 for uniformly charging thephotosensitive drum 110.

The printer unit 1007 includes the fixing device 130 for fixing thetoner image on the sheet to which the toner image has been transferred,and a sorter 132 for receiving the sheet on which a toner image is fixedvia a flapper 131. The printer unit 1007 includes an intermediate tray137 for receiving the sheet on which a toner image is fixed via theflapper 131 and feed rollers 133 to 136.

The printer unit 1007 includes a re-feed roller 138 for feeding thesheet of the intermediate tray 137 to the photosensitive drum 110 again.The flapper 131 is configured to switch a feeding destination of thetoner image-fixed sheet between the sorter 132 and the intermediate tray137. The rollers 133 to 136 are configured not to invert (i.e., multipleprinting) or invert (i.e., two-sided printing) the toner image-fixedsheet.

FIG. 3 is a block diagram illustrating a configuration of the controlunit 1006 illustrated in FIG. 2. In FIG. 3, the control unit 1006 isconnected to the scanner unit 1008, the printer unit 1007, the LAN 1005,and a public line to receive/output image data or device information.

The control unit 1006 includes a raster image processor (RIP) 2010 forrasterizing, in a bitmap image, a page description language (PDL) codeincluded in a print job received from a computer terminal on the LAN viathe LAN 1005. The control unit 1006 includes a scanner image processingunit 2011 for correcting, processing or editing image data entered fromthe scanner unit 1008. The control unit 1006 includes a printer imageprocessing unit 2012 for correcting or changing the resolution of theimage data output (printed) from the printer unit 1007, and an imagerotation unit 2013 for rotating the image data.

The control unit 1006 includes an image compression unit 2014 forcompressing/decompressing multivalued image data in Joint PhotographicExpert group (JPEG) format and binary image data in Joint Bi-level Imageexperts Group (JBIG) format, Modified Modified READ (MMR) format orModified Huffman (MH) format. The control unit 1006 includes a deviceinterface (I/F) 2015 for connecting the control unit 1006 to the scannerunit 1008 and the printer unit 1007 to perform synchronous/asynchronousconversion of image data. The control unit 1006 includes an image bus2018 for interconnecting these components to transfer image data to eachother at a high speed.

The control unit 1006 includes a CPU 2001 serving as a control unit(first control unit) for controlling the image forming apparatus 1003.The control unit 1006 includes a random access memory (RAM) 2006 servingas a system work memory for operating the CPU 2001 and also serving asan image memory for temporarily storing image data. The control unit1006 outputs via an interface unit for the operation unit 1010, imagedata to the operation unit 1010 to be displayed. The control unit 1006includes an operation unit I/F 2007 which transmits information enteredby a user of the communication system to the CPU 2001.

The control unit 1006 includes a network unit 2008 connected to the LAN1005 via the switching hub 1004 to communicate (transmit/receive) withthe PC 1002 or a computer terminal (e.g., PC 1001) on the LAN 1005. Thecontrol unit 1006 includes a modem unit 2009 connected to the publicline to communicate (transmit/receive) data with an external facsimileapparatus. The network unit 2008 receives data from the computerterminals on the LAN 1005, and processes the received data.

The control unit 1006 includes a read-only memory (ROM) 2002 for storinga boot program executed by the CPU 2001, and a hard disk drive (HDD)2003 for storing system software, image data or a software countervalue. The control unit 1006 includes a scanner/printer communicationI/F 2005 for communication with CPUs of the scanner unit 1008 and theprinter unit 1007, and a system bus 2017 for interconnecting thesecomponents.

The control unit 1006 includes an image bus I/F 2004 serving as a busbridge for interconnecting the system bus 2017 and the image bus 2018 toconvert a data structure. The control unit 1006 includes a power ON/OFFunit 2016 for supplying DC power received from the power supply unit1009 via a power supply line 2019 to predetermined circuit elements ofthe control unit 1006 via power supply lines 2020 and 2021.

The power ON/OFF unit 2016 is controlled according to a control signalreceived from the network unit 2008 via a control signal line 2023 and acontrol signal received from the CPU 2001 via a control signal line2022. The power ON/OFF unit 2016 selectively turns ON/OFF the powersupply lines 2020 and 2021. The power supply line 2020 is connected tothe CPU 2001, the ROM 2002, the HDD 2003, the image bus I/F 2004, andthe scanner/printer communication I/F 2005.

The power supply line 2020 is connected to the device I/F 2015, theimage rotation unit 2013, the image compression unit 2014, the RIP 2010,the scanner image processing unit 2011, and the printer image processingunit 2012. The power supply line 2021 is connected to the RAM 2006, theoperation unit I/F 2007, the network unit 2008, and the modem unit 2009.

The image forming apparatus 1003 illustrated in FIG. 1 performs printingprocessing as follows based on a print job transmitted from the computerterminal connected to the LAN 1005. The CPU 2001 stores in the RAM 2006print data (image data) received from the computer terminal connected tothe LAN 1005 via the network unit 2008. Then, the CPU 2001 supplies theimage data to the RIP 2010 via the image bus I/F 2004. The RIP 2010expands the image data (PDL code) in bitmap data. The image compressionunit 2014 compresses the image data to store it in the HDD 2003.

The image data (compressed bitmap data) stored in the HDD 2003 issupplied to the image compression unit 2014 via the image bus I/F 2004.The image compression unit 2014 decompresses the supplied image data(compressed bitmap data). The printer image processing unit 2012performs correction of the printer or resolution-conversion for theimage data.

The image rotation unit 2013 rotates the image data when necessary.Then, the variously processed image data is sent as print data to theprinter unit 1007 via the device I/F 2015 to be printed on a sheet bythe printer unit 1007.

The image forming apparatus 1003 is operable in a deep sleep mode (oneof power-saving modes). In a normal mode, the power supply unit 1009supplies power to the power ON/OFF unit 2016 via the power supply line2019. The CPU 2001 controls the power ON/OFF unit 2016 so that each ofthe power supply lines 2020 and 2021 is turned ON. In this case, thepower supply unit 1009 supplies power to both of the CPU 2001 and thenetwork unit 2008.

In the deep sleep mode, the power supply unit 1009 supplies power to thepower ON/OFF unit 2016 via the power supply line 2019. The CPU 2001controls the power ON/OFF unit 2016 so that the power supply line 2020is turned OFF while the power supply line 2021 is turned ON.

In this case, power supplied to the main circuit components includingthe CPU 2001 of the control unit 1006 is cut off. Thus, powerconsumption of the image forming apparatus 1003 can be significantlyreduced.

Upon receiving data such as a print job from the computer terminal onthe LAN 1005, the network unit 2008 can control the power ON/OFF unit2016 to return to the normal mode.

In the deep sleep mode, the power supplied to the CPU 2001 is cut off.However, other arrangements may be employed. For example, the powersupplied to the CPU 2001 may be reduced lower than that in the normalmode. In this case, the CPU 2001 has executable processing limited morethan that in the normal mode. The limited processing includes at leastprocessing of data received from the computer terminal of the LAN 1005by the network unit 2008.

In the deep sleep mode, power has been supplied to the RAM 2006 from thepower supply unit 1009. Thus, the RAM 2006 performs a self-refreshingoperation to back up a system program.

In the above description, the network unit 2008 switches the powersupply mode from the deep sleep mode to the normal mode. However, otherarrangements may be employed. Specifically, not only the network unit2008 but also the modem unit 2009 or the operation unit I/F 2007 mayswitch the mode from the deep sleep mode to the normal mode. The formercase enables facsimile communication, which uses the public line. Thelatter case enables reception of an instruction from the user of theoperation unit I/F 1010.

The image forming apparatus 1003 illustrated in FIG. 1 returns from thedeep sleep mode to the normal mode as follows.

For example, upon receiving a print job from the PC 1002, the networkunit 2008 analyzes the print job to determine whether a packet receivedas the print job contains a data sequence corresponding to a physicaladdress unique to its own apparatus. Upon detecting the data sequencecorresponding to the own apparatus, the network unit 2008 controls thepower PN/OFF unit 2016 via the control signal line 2023 to turn thepower supply line 2021 ON, and activates the CPU 2001.

The CPU 2001 determines whether the activation of the CPU 2001 is causedby a return from the deep sleep mode to the normal mode based on thepower ON/OFF unit 2016. Upon determining that it is caused by a returnfrom the deep sleep mode to the normal mode, the CPU 2001 starts a bootsequence.

In this case, the CPU 2001 uses the system program backed up by the RAM2006 when the mode has been switched to the deep sleep mode withoutperforming a sequence for downloading the system program from the HDD2003 to the RAM 2006. Thus, the control unit 1006 set in the normal modecauses the printer unit 1007 to start printing in response to the printjob from the computer terminal of the LAN 1005.

FIG. 4 illustrates a software configuration of a program executed by theCPU 2001. The program illustrated in FIG. 4 is stored in the HDD 2003,and the CPU 2001 executes a boot program to read the program from theHDD 2003 to the RAM 2006.

In FIG. 4, an operating system program (OS) 4000 operates as a basicprogram for executing various driver programs described below. A RAMcontrol driver 4001 is a program for controlling the RAM 2006 based onan instruction from the OS 4000.

An operation unit I/F driver 4002 is a program for controlling theoperation unit I/F 2007 based on an instruction from the OS 4000. Anetwork unit control driver 4003 is a program for controlling thenetwork unit 2008 based on an instruction of the OS 4000.

A modem unit control driver 4004 is a program for controlling the modemunit 2009 based on an instruction from the OS 4000. A scanner unitcontrol driver 4005 is a program for controlling the scanner unit 1008based on an instruction from the OS 4000. A printer unit control driver4006 is a program for controlling the printer unit 1007 based on aninstruction from the OS 4000.

The CPU 2001 executes the OS 4000 read in the RAM 2006 to control theunits including the RAM 2006, the operation I/F 2007, the network unit2008, the modem unit 2009, the printer unit 1007, and the scanner unit1008. The programs 4001 to 4006 can operate in parallel on the OS 4000.The CPU 2001 executes the programs while switching the programs executedin a time-division manner so that the programs 4001 to 4006 can operatein parallel.

FIG. 5 is a block diagram illustrating a configuration of the networkunit 2008. The network unit 2008 includes a CPU 301, a MAC/PHY 302, abus I/F 303, a ROM 304, and a RAM 305, which are interconnected via abus. The network unit 2008 is connected to the system bus 2017 via theswitching hub 1004.

The MAC/PHY 302 functions as a second packet processing unit fortransmitting/receiving packet data with the switching hub 1004. The CPU301 functions as a second control unit for controlling the MAC/PHY 302(the second packet processing unit).

The ROM 304 stores a wake-on-LAN pattern (WOL pattern). The CPU 301determines, when the image forming apparatus 1003 operates in the deepsleep mode, whether a packet received by the MAC/PHY 302 via the LAN1005 matches the WOL pattern stored in the ROM 304.

Upon determining that the packet received by the MAC/PHY 302 matches theWOL pattern, the CPU 301 instructs the power supply unit 1009 so thatthe power ON/OFF unit 2016 resumes power supply to the CPU 2001 via thepower supply line 2020.

The ROM 302 stores a substitute response pattern. The RAM 305 storesresponse data corresponding to the substitute response pattern. Thisresponse data includes, for example, status information of the imageforming apparatus 1003 (e.g., information indicating an operation modeof the image forming apparatus 1003 or information indicating theremaining amount of sheets).

The CPU 301 determines, when the image forming apparatus 1003 operatesin the deep sleep mode, whether the packet received by the MAC/PHY 302via the LAN 1005 matches a substitute response pattern stored in the ROM304. Upon determining that the packet received by the MAC/PHY 302matches the substitute response pattern, the CPU 301 reads from the RAM305 the response data corresponding to the substitute response pattern.The CPU 301 transmits the response data read from the RAM 305 to thecomputer terminal on the LAN 1005, which is a transmission source of thesubstitute response pattern.

The CPU 301 issues no instruction to the power supply unit 1009 forcausing the power ON/OFF unit 2016 to resume power supply to the CPU2001 via the power supply line 2020 even when the CPU 301 detects thesubstitute response pattern. Thus, the image forming apparatus 1003 canexecute response processing while maintaining the deep sleep modewithout returning to the normal mode from the deep sleep mode when itreceives the substitute response pattern to respond.

The network unit 2008 can execute communication complying with Ethernet(registered trademark) standard. The network unit 2008 can carry outcommunication in a plurality of types of communication modes, and cancommunicate with the switching hub 1004, for example, at one ofcommunication speeds of 10 Mbps, 100 Mbps, and 1000 Mbps. The switchinghub 1004 complies with the Ethernet standard, and can performcommunication at one of speeds of 10 Mbps, 100 Mbps, and 1000 Mbps.

FIG. 9 is a block diagram illustrating a configuration of the switchinghub 1004. The switching hub 1004 includes three connection ports (i.e.,1st to 3rd ports 904 to 906). The switching hub 1004 includes a relaycircuit 903 for relaying among the ports.

Under control of the CPU 901, the relay circuit 903 can optionallyswitch connection among the ports. The CPU 901 functions as a firstpacket processing unit for transmitting/receiving packet data via theports 904 to 906. The RAM 902 stores a VLAN database illustrated in FIG.6 described below. The VLAN database includes data indicating, asdescribed below, relationship between identification information (MACaddress in the exemplary embodiment) for identifying a computer terminalwhich can participate in a virtual network (VLAN) of the switching huband a type of VLAN.

The CPU 901 determines whether information included in the packet datareceived from each port matches identification information stored in theVLAN database. Upon determining the matching, the CPU 901 manages theterminal, which has transmitted the packet data to the port, toparticipate in the virtual network corresponding to the matchedidentification information.

The switching hub 1004 is presumed to be capable of constituting adynamic virtual local area network (VLAN). A VLAN technique virtuallydivides a plurality of computer terminals of a network physicallyconnected using a network device such as a switching hub into aplurality of groups (virtual network), and manages the groups as theybelong to different LANs.

The VLAN technique includes a technique for configuring a VLAN bygrouping a plurality of ports of the switching hub (static VLANtechnique). According to this technique, for example, the switching hubmanages two terminals each connected to the 1st and 2nd ports asterminals constituting a VLAN 1, and one terminal connected to the 3rdport as a terminal constituting a VLAN 2.

The VLAN technique includes a dynamic VLAN technique. According to thedynamic VLAN technique, the switching hub virtually divides a pluralityof computer terminals into a plurality of groups to manage them based oninformation obtained from each of the plurality of computer terminalsconnected to the switching hub.

For example, in the case of the MAC based VLAN technique, MAC addressesare obtained from computer terminals connected to the switching hub, andthe switching hub manages to which VLAN a computer terminal with a MACaddress belongs.

For example, in the case of the subnet based VLAN technique, IPaddresses are obtained from computer terminals connected to theswitching hub, and the switching hub manages to which VLAN a computerterminal with an IP address belongs.

For example, in the case of the user based VLAN technique, userinformation is obtained from computer terminals connected to theswitching hub, and the switching hub manages to which VLAN a computerterminal of which user information belongs.

The description will continue assuming that the switching hub 1004illustrated in FIG. 1 complies with the MAC based VLAN.

In FIG. 1, the PCs 1001 and 1002 and the image forming apparatus 1003are connected to the switching hub 1004. The PC 1001 is connected to aport 1 of the switching hub, the PC 1002 is connected to a port 2, andthe image forming apparatus 1003 is connected to a port 3.

The switching hub 1004 performs management in a manner that the PC 1002belongs to the first VLAN (VLAN 1), and the PC 1001 and the imageforming apparatus 1003 belong to the second VLAN (VLAN 2). In this case,the VLAN database illustrated in FIG. 6 is stored in a memory (notillustrated) of the switching hub 1004.

In FIG. 6, the PC 1001 having a MAC address of 000085000001 and theimage forming apparatus 1003 having a MAC address of 00085000003 aremanaged as the VLAN 1 by the switching hub. The PC 1002 having a MACaddress of 000085000002 is managed as the VLAN 2.

When the switching hub 1004 performs management as illustrated in FIG.5, even if the PC 1002 designates the IP address of the PC 1001 torequest data transmission or reception, the PCs 1002 and 1001 belong todifferent VLANs. Thus, no data is transmitted or received between thePCs 1002 and 1001.

Upon receiving a broadcast packet from the PC 1001, the switching hub1004 transmits the broadcast packet to the image forming apparatus 1003,which belongs to the same VLAN (VLAN 2) as that of the PC 1001. On theother hand, the switching hub 1004 transmits no broadcast packet to thePC 1002, which belongs to a VLAN (VLAN 1) different from that of the PC1001.

In FIG. 6, the PC 1001 having a MAC address of 000085000001 is in a VLANnonparticipation state. However, the above description assumes that thePC 1001 is in a participation state.

In the VLAN database illustrated in FIG. 6, the VLAN participation stateindicates whether a computer terminal identified by a MAC addressparticipates in the VLAN. As described above, to enable participation ofa certain computer terminal in the VLAN, simple establishment of acommunication link with the switching hub 1004 is not enough. In thecommunication link established state, the switching hub 1004 has toreceive a MAC address of the computer terminal.

It is presumed that the switching hub 1004 has received a MAC address ofa computer terminal in a link-up state where a communication link withthe computer terminal has been established. In this case, the switchinghub 1004 performs management to switch a VLAN participation statecorresponding to the MAC address from nonparticipation to participation.

An operation performed by the image forming apparatus 1003 connected tothe switching hub 1004 compatible to the MAC based VLAN will bedescribed.

FIG. 7 is a flowchart illustrating an operation performed by the CPU2001 of the control unit 1006. FIG. 8 is a flowchart illustrating anoperation performed by the CPU 301 of the network unit 2008.

The operation of the flowchart of FIG. 7 is started by starting powersupplying from the power supply unit 1009 to the CPU 2001.

There are following two cases for starting power supplying from thepower supply unit 1009 to the CPU 2001. One is when a main switch (notillustrated) of the image forming apparatus 1003 is switched from OFF toON. The other is when the operation mode of the image forming apparatus1003 is switched from the deep sleep mode to the normal mode while themain switch of the image forming apparatus 1003 is the ON state.

In step S701, the CPU 2001 reads the boot program stored in the ROM 2002to expand it on the RAN 2006, and executes the boot program expanded onthe RAM 2006. The CPU 2001 reads, by executing the boot program, the OS4000 and various control drivers 4001 to 4006 illustrated in FIG. 4 fromthe HDD 2002 to expand them on the RAM 2006. Then, the CPU 2001 operatesthe OS 4000 and the network unit control driver 4003 executed on the OS4000 expanded on the RAM 2006 to execute each step.

In step S702, the OS 4000 determines whether the image forming apparatus1003 has returned from the deep sleep mode to the normal mode, orwhether the main switch has been switched from OFF to ON. The OS 4000refers to flag information stored in the RAM 2006 to executedetermination of step S702.

In step S707 described below, the OS 4000 stores information indicatinga change to the deep sleep mode as flag information when changing to thedeep sleep mode. The OS 4000 determines, if information indicating achange to the deep sleep mode has been stored as flag information, thatthe mode has returned from the deep sleep mode to the normal mode.

If the return to the deep sleep mode is determined (YES in step S702),the processing proceeds to step S709. Otherwise, the processing proceedsto step S703.

In step S703, the network unit control driver 4003 gives instruction tothe network unit 2008 to initialize the network unit 2008. Specifically,the network unit control driver 4003 sets a register of the CPU 301 tocancel a reset signal to the CPU 301. To initialize the MAC/PHY 302, thenetwork unit control driver 4003 sets a register of the MAC/PHY 302.Thereby, the network unit 2008 is initialized to be capable ofcommunicating with the CPU 2001 and the switching hub 1004.

It is presumed that the MAC/PHY 302 of the network unit 2008 and theswitching hub 1004 are both compatible to an auto-negotiation function.In the register of the MAC/PHY 302, whether the auto-negotiationfunction is turned ON/OFF can be set. It is presumed that in theregister of the MAC/PHY 302, as default setting when the network unit2008 is initialized, the auto-negotiation function is turned ON.

In this case, the MAC/PHY 302 transmits a pulse signal called a fastlink pulse (FLP) to the switching hub 1004 in response to initializationof the network unit 2008. The FLP is transmitted from the switching hub1004 to the MAC/PHY 302. The MAC/PHY 302 can recognize a communicationspeed to which the switching hub 1004 is compatible based on the FLPreceived from the switching hub 1004.

In the exemplary embodiment, the MAC/PHY 302 and the switching hub 1004are both compatible to communication speeds of 10 Mbps, 100 Mbps, and1000 Mbps. Thus, the MAC/PHY 302 determines 1000 Mbs that is a highestcommunicable speed for both as a communication speed to link up with theswitching hub 1004. The linking-up means a communication linkestablished state or a data transmission/reception enable state.Linking-down means a communication link non-established state or a datatransmission/reception disable state. The communication link establishedstate means a state where not only certain information can betransmitted/received but also packet data can be transmitted/received.

In step S704, the network unit control driver 4003 transmits a MACaddress, which is a physical address allocated to the network unit 2003,to the switching hub 1004 via the network unit 2008.

In step S703, the CPU 2001 performs control to generate a packetcontaining a MAC address, and to transmit the generated packet to theswitching hub 1004 via the MAC/PHY 302 of the network unit 2008. In stepS704, the CPU 301 of the network unit 2008 is not involved in packettransmission.

Upon receiving the MAC address (000085000003) of the network unit 2003from the image forming apparatus 103, the switching hub 1004 switches aVLAN participation state of the received MAC address from“non-participation” to “participation”. The switching hub 1004accordingly performs management assuming that a computer terminalcorresponding to the received MAC address has participated in the VLAN.

In step S709, the network unit control driver 4003 gives an instructionto the network unit 2008 to change the register of the MAC/PHY 302 ofthe network unit 2008. Specifically, the setting to turn OFF theauto-negotiation function in the MAC/PHY 302 is changed to setting toturn it ON.

In this case, the MAC/PHY 302 transmits a pulse signal called a FLP tothe switching hub 1004 according to turning-ON of the auto-negotiationfunction. The FLP is transmitted from the switching hub 1004 to theMAC/PHY 302. The MAC/PHY 302 can recognize that the switching hub 1004is compatible to a communication speed based on the FLP received fromthe switching hub 1004.

In the exemplary embodiment, the MAC/PHY 302 and the switching hub 1004can both be compatible to communication speeds of 10 Mbps, 100 Mbps, and1000 Mbps. The MAC/PHY 302 accordingly determines 1000 Mbps, which is ahighest compatible speed for both, as a communication speed to link upwith the switching hub 1004.

In step S710, the network unit control driver 4003 transmits a MACaddress, which is a physical address allocated to the network unit 2003,to the switching hub 1004 via the network unit 2008.

In step S703, the CPU 2001 performs control to generate a packetincluding a MAC address and to transmit the generated packet to theswitching hub 1004 via the MAC/PHY 302 of the network unit 2008. In stepS710, the CPU 301 of the network unit 2008 is not involved in packettransmission.

In step S705, the OS 4000 determines whether a sleep change condition(switching condition) has been established to switch the image formingapparatus 1003 to the deep sleep mode, and the processing proceeds tostep S706 if established (YES in step S705).

If the sleep change condition is not established (NO in step S705), theOS 4000 executes step S705 again. In this case, the CPU 2001 thatexecutes the OS 4000 functions as a first determination unit fordetermining whether the switching condition has been established.

The OS 4000 determines that the sleep change condition has beenestablished, for example, if a state in which neither of the controldrivers 4001 to 4006 is executed on the OS 4000 continues for apredetermine period (e.g., 15 minutes). For example, if a state wherethe network unit 2008 receives no packet and the operation unit 1010 isnot operated continues for a predetermined period, the OS 4000determines that the sleep change condition has been established.

In step S706, the network unit control driver 4003 notifies the CPU 301of the network unit 2008 that the image forming apparatus 1003 ischanged to the deep sleep mode. In this case, the network unit controldriver 4003 notifies the CPU 301 of information indicating a speed ofcommunication carried out between the network unit 2008 and theswitching hub 1004 after the change to the deep sleep mode.Specifically, the network unit control driver 4003 notifies the CPU 301of information indicating a communication speed of 10 Mbps.

In step S707, the network unit control driver 4003 changes a connectionstate between the MAC/PHY 302 and the switching hub 1004 from a link-upstate where a communication link has been established to a link-downstate where no communication link has been established. Specifically,the network unit control driver 4003 sets the register of the MAC/PHY302 to a link-down state. After this register setting, the MAC/PHY 302sets a communication state with the switching hub 1004 to a link-downstate.

The switching hub 1004 periodically monitors a link state with the imageforming apparatus 1003, and switches a VLAN participation state of a MACaddress corresponding to the image forming apparatus 302 from“participation” to “nonparticipation” when the link-down state isdetected. The switching hub 1004 accordingly recognizes anonparticipation state of the image forming apparatus 1003 in the VLAN1of the switching hub 1004.

The setting to turn ON the auto-negotiation function has been set in theMAC/PHY 302. Thus, the setting is changed to turn the function OFF. Thischange is made, in the deep sleep mode, to set a speed of communicationcarried out between the network unit 2008 and the switching hub 1004lower than that in the normal mode.

In step S708, the CPU 2001 transmits a signal to the power OFF/ON unit2016 via the power control signal line 2022 for cutting off powersupplied via the power supply line 2020. The power OFF/ON unit 2016,which has received the signal, cuts off power supplied to the CPU 2001via the power supply line 2020. Thus, the image forming apparatus 1003changes to the deep sleep mode.

The operation of the image forming apparatus 1003 to change from thedeep sleep mode to the normal mode is as described above.

Referring to FIG. 8, an operation performed by the CPU 301 of thenetwork unit 2008 will be described below.

Changing the main switch (not illustrated) of the image formingapparatus 1003 from OFF to ON starts supplying power from the powersupply unit 1009 to the CPU 301. An operation of a flowchart illustratedin FIG. 8 is started when the network unit control driver 4003 cancels areset signal of the CPU 301.

In step S801, the CPU 301 reads a program from the ROM 302 to expand itin the RAM 305, and executes the program expanded in the RAM 305.Executing this program initializes the network unit 2008 to acommunicable state with the CPU 2001 and the switching hub 1004.

After initialization of the network unit 2008, as described above, theMAC/PHY 302 determines 1000 Mbps, which is a highest communicable speedbetween the MAC/PHY 302 and the switching hub 1004, as a communicationspeed. The MAC/PHY 302 links up with the switching hub 1004 at thedetermined communication speed.

In step S802, the CPU 301 determines whether it has received anotification of a change to the deep sleep mode from the network unitcontrol driver 4003 (CPU 2001), and the processing proceeds to step S803if received (YES in step S802).

The CPU 301 receives from the CPU 2001 the notification of the change tothe deep sleep mode together with information indicating a speed ofcommunication (communication speed information) carried out between thenetwork unit 2008 and the switching hub 1004 after the change to thedeep sleep mode.

In step S803, the CPU 301 checks whether the network unit control driver4003 (CPU 2001) has set the register of the MAC/PHY 302. The CPU 301accordingly determines whether the MAC/PHY 302 has been set in alink-down state. The CPU 301 proceeds to step S804 if it determines thatthe MAC/PHY 302 has been set in the link-down state (YES in step S803).The register setting of the MAC/PHY 302 is changed by the CPU 2001 toturn OFF the auto-negotiation function.

In step S804, the CPU 301 switches a connection state between theMAC/PHY 302 and the switch HUB 1004 from the link-down state to alink-up state at a communication speed indicated by the communicationspeed information received from the CPU 2001 in step S802. The CPU 2001(network unit control driver 4003) has designated 10 Mbps lower than acommunication speed (1000 Mbps) in the normal mode to save power. Thus,the CPU 301 notifies the switching hub 1004 of linking-up at thecommunication speed of 10 Mbps. According to this notification, theMAC/PHY 302 and the switching hub 1004 are set in a linked-up state atthe communication speed of 10 Mbps.

In step S805, the CPU 301 transmits a MAC address which is a physicaladdress allocated to the network unit 2003 to the switching hub 1004 viathe MAC/PHY 302. In step S804, the CPU 301 performs control to generatea packet containing a MAC address and to transmit the generated packetto the switching hub 1004 via the MAC/PHY 302.

In step S805, the CPU 2001 is not involved in packet transmission. TheMAC address is information necessary when the switching hub 1004 causesthe image forming apparatus 1003 to participate in the VLAN 1.

Upon receiving the MAC address (000085000003) of the network unit 2003from the image forming apparatus 1003, the switching hub 1004 changes aVLAN participation state of the received MAC address from“nonparticipation” to “participation”. The switching hub 1004accordingly recognizes a participation state of a computer terminal(image forming apparatus 1003) corresponding to the received MAC addressin the VLAN 1 of the switching hub 1004.

In step S806, the CPU 301 determines whether it has detected a sleepreturn cause (whether a return condition has been established). If thesleep return cause is detected (YES in step S806), the processingproceeds to step S807.

For example, the following two can be sleep return causes. One is a casewhere the MAC/PHY 302 has received a WOL pattern via the LAN 1005. TheCPU 301 determines whether a packet received by the MAC/PHY 302 matchesa WOL pattern stored in the ROM 304. If matched, the CPU 301 hasdetected a sleep return cause.

The other is a case where a LAN cable is inserted into/pulled out of aLAN socket of the network unit 2008. The CPU 301 determines whether theLAN cable has been inserted/pulled out, and has detected a sleep returncause if it determines that the LAN cable has been inserted/pulled out.In step S806, the CPU 301 functions as a second determination unit todetermine whether a return condition has been established to return theimage forming apparatus 1003 from the deep sleep mode as a power savingmode to the normal mode.

In step S807, the CPU 301 transmits a signal for turning ON the powersupply line 2020 to the power ON/OFF unit 2016 via the control signalline 2023 to start supplying power to the CPU 2001.

In step S808, the CPU 301 sets the register of the MAC/PHY 302 to set alink-state between the MAC/PHY 302 and the switching hub 1004 to be alink-down state. After the setting of the register, the MAC/PHY 302 setsa communication state with the switching hub 1004 to a link-down state.

The switching hub 1004 periodically monitors its link state with theimage forming apparatus 1003, and switches, when the link-down state isdetected, a VLAN participation state of a MAC address corresponding tothe image forming apparatus 1003 from “participation” to“nonparticipation”. The switching hub 1004 accordingly recognizes anonparticipation state of the image forming apparatus 1003 in the VLANof the switching hub 1004.

As described above, the first exemplary embodiment enables securetransmission of information (MAC address) necessary for participation ofthe image forming apparatus 1003 in the virtual network (MAC addressbased dynamic VLAN) to the switching hub while saving power of the imageforming apparatus 1003 as a communication apparatus. Thus, the imageforming apparatus 1003 can participate in the dynamic VLAN while keepingits power consumption low in the deep sleep mode which is a power savingmode.

Average power consumed in the operated state of the CPU 2001 is higherthan that consumed in the operated state of the CPU 301. The CPU 2001notifies, during a change to the power saving mode, the network unit2008 of a change to the sleep mode and a communication speed, but it isnot involved in MAC address transmission. Thus, as compared with a casewhere the CPU 2001 is involved in MAC address transmission, power savingcan be achieved since power supplied to the CPU 2001 is cut offpromptly.

In the above description, the switching hub 1004 is compatible to theMAC base VLAN which is a dynamic VLAN. However, other arrangements maybe employed.

For example, the switching hub 1004 may be compatible to a subnet basedVLAN, which is a dynamic VLAN. In this case, the switching hub 1004stores a database similar to that illustrated in FIG. 10 as a VLANdatabase in the RAM 902. The image forming apparatus 1003 establishes acommunication link with the switching hub 1004 to set a link-up state,and then transmits an IP address allocated thereto to participate in theVLAN 1 to the switching hub 1004.

After the communication link with the image forming apparatus 1003 hasbeen established to be the link-up state, the switching hub 1004receives an IP address (192.168.12.1) of the image forming apparatus1003. In this case, the switching hub 1004 performs management as theimage forming apparatus 1003 has participated in the VLAN 1.

For example, the switching hub 1004 may be compatible to a user basedVLAN, which is a dynamic VLAN. In this case, the switching hub 1004stores a database similar to that illustrated in FIG. 11 as a VLANdatabase in the RAM 902. The image forming apparatus 1003 establishes acommunication link with the switching hub 1004 to be a link-up state.

Then, the image forming apparatus 1003 transmits a user ID (userinformation) to identify a user logging-in the image forming apparatus1003 to participate in the VLAN 1 to the switching hub 1004. Afterhaving been set in the linked-up state by establishing the communicationlink with the image forming apparatus 1003, the switching hub 1004receives the user ID (USER-C) from the image forming apparatus 1003. Inthis case, the switching hub 1004 performs management as the imageforming apparatus 1003 has participated in the VLAN 1.

In the above description, the switching hub 1004 is compatible to thedynamic VLAN (e.g., MAC based VLAN). However, other arrangements may beemployed. For example, a switching hub 1004 that is not compatible to adynamic VLAN may be used.

Then, the image forming apparatus 1003 obtains, from the switching hub1004, information indicating whether the switching hub 1004 iscompatible to a dynamic VLAN. Based on the obtained information, theimage forming apparatus 1003 determines whether the switching hub 1004is compatible to a dynamic VLAN. If the image forming apparatus 1003determines that the switching hub 1004 is not compatible to the dynamicVLAN, the CPU 2001 does not execute steps S704 and S710. The CPU 301does not execute step S805. Thus, the processing can be appropriatelycarried out depending on whether the switching hub 1004 is compatible tothe dynamic VLAN.

The present invention can be achieved by supplying a storage mediumstoring software program codes for realizing the functions of theexemplary embodiment to a system or an apparatus. In this case, acomputer of the system or the apparatus reads and executes the programcodes stored in the storage medium to realize the functions of theexemplary embodiment. In this case, the program codes read from thestorage medium realize the functions of the exemplary embodimentthemselves, and the storage medium storing the program codes is withinthe invention.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all modifications, equivalent structures, and functions.

What is claimed is:
 1. A communication apparatus comprising: acommunication unit configured to communicate with an external apparatusat any one of a plurality of communication speeds; a processing unitconfigured to process data received via the communication unit from theexternal apparatus; a changing unit configured to, in a case where thereis an input of an instruction for returning the communication apparatusfrom a power saving mode, change the communication speed of thecommunication unit into a predetermined speed among at least onecommunication speed at which both the external apparatus and thecommunication apparatus are capable of performing communication; and acontrol unit configured to control the communication unit so as totransmit identification information of the communication apparatus tothe external apparatus in a case of a change in the communication speedof the communication unit into the predetermined speed by the changingunit.